GEOCHEMISTRY AND ITS GEOLOGICAL IMPLICATION OF THE PERMIAN GRANITE IN NUOMIN, DAXINGANLING REGION

The Nuomin area in Daxinganling is tectonically located in the east section of the Xingan-Mongolian orogenic belt, where large volumes of Permian granitic rocks, mainly monzogranite and moyite, are developed. Major element analysis shows high SiO₂ and alkali content, slightly high K₂O content and low MgO and CaO contents. Trace element study demonstrates the enrichment of Rb, Th, K, Nd and Cs, and depletion of Ba, U, Nb, Sr, P and Ti. The samples are enriched in LREE and depleted in HREE, with apparent negative Eu anomalies, suggesting a high degree of fractionation. The granites generally belong to the high-K calc-alkaline series. Petrogeochemistry shows that the granites are quite similar to S-type granite. They are most likely resulted from the partial melting of homologous crust, probably derived from metamorphic greywacke and intermediate volcanic rocks. According to the discrimination diagrams of R1-R2, Rb-(Yb+ Nb) and Rb-(Yb+Ta), the granites are generated in the stage of post-collision after the collision between Xingan block and Songnen block.